Bob,
Reaching back in the memory banks to the power supply design days
tells me I've seen similar problems. The problem you describe
sounds like it could be generated in the power supply rectifier
diode(s). A little work with an oscilloscope can tell you fairly
quickly. If you can modify the power supply, relaying out the pc
board is the best solution, next, if the pc re-layout is not
plausible, then an R/C snubber across the rectifier diodes can be
effective. If you can't or don't wish to modify the power supply,
then a balun in the power supply leads (+5 & rtn lines both going
through a high frequency torroid core for as many turns as you can
or until the noise pulse is at an acceptable level) is your next
best bet. Is the power supply compliant with the EMC directive ?
How long exactly are the leads from the power supply and the cage
and what gauge wire are they ?
Hope this leads you to a speedy solution.
Dan Teninty P.E.
Senior Engineering Specialist
Systems Safety
Raytheon Systems Company
Tucson, AZ
[email protected]
______________________________ Reply Separator _________________________________
Subject: Noise in Power Lead
Author: [email protected] at mime
List-Post: [email protected]
Date: 1/6/98 7:21 AM
Happy New Year All,
I have an interesting noise problem brought to me.
The noise is a 500-900 mV pulse seen at 50 MHz on a
power lead from a DC to DC converter (48V to 5V) to a
VME cage.
There were two scenarios: first, both the power supply
and the cage are earth-grounded, and the pulse is seen
at both the power supply and the cage. Second, the cage
is left floating, and the pulse is only seen at the
power supply.
The noise seems to be a ring, and the leads between the
supply and cage are fairly long.
Has anybody seen something like this before, or does anybody
have any suggestions or comments?
We have several ideas, but not much time.
The frequency and the fact that the pulse reaches almost a volt
concerns us greatly.
Thanks in advance,
Bob Tims
Standards and Compliance
[email protected]
The opinions expressed in this correspondence in no way reflect
the opinions of Ericsson Inc.
RCIC - http://www.rcic.com
Regulatory Compliance Information Center
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Date: Tue, 06 Jan 1998 10:21:01 -0500
From: Bob Tims <[email protected]>
Subject: Noise in Power Lead
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